Process for shaping and sharpening a rotatable surgical shaver blade

ABSTRACT

A process for simultaneously shaping and sharpening a cutting widow at the distal end of a tubular member of a rotary blade assembly. The assembly is provided with a stationary elongated outer tube, having a cutting window at its distal tip and includes a rotatable elongated inner tube having a cutting means at its distal tip. The window in the outer tube has a curvilinear profile defined by a peripheral rim surrounded entirely by a land surface which is inclined relative to the rim. The inclination of the land produces an area which tapers from a full thickness, where the land is adjacent to the cylindrical wall of the outer tube, to a sharp edge around the periphery of the window. The curvilinear window is produced by a manufacturing process which creates the window opening with a sharpened periphery at the same time that the land surrounding the opening is inclined. A preferred embodiment utilizes electrochemical grinding of the distal ends of the tubular member by a tool having a rotatable wheel with a perimeter in the shape of a groove of predetermined arcuate profile.

This is a divisional continuation Application Ser. No. 08/791,233, filedJan. 30, 1997 now U.S. Pat No. 5,104,063 WHICH IN TURN IS ACONTINUATION-IN-PART OF Ser. No. 08/636,990 FILED Apr. 10, 1996, NOWABANDONED.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

The invention relates to elongated, powered surgical instruments for usein endoscopic tissue resection. More particularly, the invention relatesto an instrument having an elongated inner tube rotatably situatedwithin an elongated stationary outer tube, both inner and outer tubeshaving, at their distal ends, cutting apertures which cooperate toresect or otherwise affect tissue during endoscopic surgical procedures.Still more particularly, the invention relates to the method ofmanufacturing the cutting aperture at the distal end of an elongatedtubular member of a rotatable surgical instrument.

DESCRIPTION OF THE PRIOR ART

The use of elongated surgical cutting instruments has become wellaccepted in performing closed surgery such as arthroscopic or, moregenerally, endoscopic surgery. In closed surgery, access to the surgicalsite is gained via one or more portals, and instruments used in thesurgical procedure must be elongated to permit the distal ends of theinstruments to reach the surgical site. Surgical cutting instruments foruse in closed surgery--also known as "shavers"--conventionally have astraight, elongated outer tubular member terminating at a distal endhaving an opening in the end or side wall (or both) to form a cuttingport or window and a straight, elongated inner tubular memberconcentrically disposed in the outer tubular member and having a distalend disposed adjacent the opening in the distal end of the outer tubularmember. The distal end of the inner tubular member has a surface or edgefor engaging tissue via the opening in the outer tubular member and inmany cases (but not all) cooperates with the opening to shear, cut ortrim tissue. In some cases, such as burrs, the opening in the outer tubemerely allows access to the tissue and does not otherwise cooperate toresect tissue. The inner tubular member is rotatably driven about itsaxis from its proximal end, normally via a handpiece having a smallelectric motor which is controlled by finger actuated switches on thehandpiece, a foot switch or switches on a console supplying power to thehandpiece. The distal end of the inner tubular member can have variousconfigurations depending upon the surgical procedure to be performed,and the opening in the distal end of the outer tubular member has aconfiguration to cooperate with the particular configuration of thedistal end of the inner tubular member. For example, the inner and outertubular members can be configured to produce whisker cutting, synovialresection, arthroplasty burring or abrading, side cutting, meniscuscutting, trimming, full radius resection, end cutting and the like, andthe various configurations are referred to generically as shaver blades.Cut tissue is aspirated through the hollow lumen of the inner tubularmember to be collected via a vacuum tube communicating with thehandpiece.

The aforementioned elongated surgical cutting instruments have also beenproduced in angled configurations in which the distal tips of the innerand outer members are aligned and offset or bent at either a fixed orvariable angle from the proximal ends of the aligned inner and outermembers. Examples of fixed and variable angle rotary surgicalinstruments are shown in U.S. Pat. Nos. 4,646,738 (Trott) and 5,411,514(Fucci et al.), both assigned to the assignee hereof, and incorporatedby reference herein. In other respects the operation of fixed andvariable angle shavers is largely the same as that of the straightshavers described above.

One parameter affecting the efficiency of operation of shaver blades issharpness of the edges of the windows. Various prior art designs areknown to have differing degrees of sharpness of both the inner cuttingedges and the periphery of the outer window. The present invention isconcerned with the design and manufacture of an outer tubular memberhaving a sharpened window periphery.

It is known that improved resection efficiency is achieved by sharpeningthe cutting edges and this is true of conventional scissors as well asendoscopic shavers although the manufacture of the latter isconsiderably more difficult. The smaller the included angle of thecutting edge, the sharper the edge. Clearly, below a certain limit theedge becomes too delicate to be practical. When applied to the tubularmembers of cylindrical, rotating shavers, the cutting edges on the innermember and the periphery of the outer window are the cooperating edgeswhich should have the smallest included angles in order to produce sharpedges. However, this must be balanced with cost and speed ofmanufacture. In prior art designs, the outer window is sometimes formedby simply grinding or milling an opening at the distal tip of the outertube, the opening lying in a plane angled relative to the tube axis.Thus, the outer window faces toward the end of the tube as well astoward the side. It will be understood that this process produces agenerally elliptical window periphery which has a lower included angleat its proximal end and a larger included angle at its distal end. Aland surface surrounds the periphery and is angled (in the cuttingplane) such that the inner rim of the land defines the sharpened cuttingedge of the outer member. The formation of this type of outer windowcould be achieved by a variety of two-dimensional through-cuttingprocesses such as wire EDM (electrical discharge machining), ram EDM,conventional or electrochemical grinding or milling. For certainpurposes, this type of cutting window may be sufficient, however, it isknown that subjecting the land surface to additional processing canproduce a sometimes more preferable "three-dimensional" window shape andsharper edge. The term "three-dimensional" is used to distinguish theopening from one formed by a simple planar cut through the tip of atube: the periphery of the latter lies only in a two-dimensional planewhile the periphery of the former also extends above and below thisplane. However, the additional steps required to produce such sharpnessentail the use of either a tool having a complex contour or a machiningprocess capable of complex contouring motions (e.g., a computernumerical control (CNC) machine). Additionally, practical manufacture ofthese devices would be hampered because simultaneous production ofseveral blades is more difficult with such processes, if at allpossible.

It is accordingly an object of this invention to produce an outer memberof a shaver blade assembly in which the window of the outer member has asharpened periphery.

It is also an object of this invention to produce a shaver bladeassembly having an outer member with a sharpened window formed by aperipheral land surface angled to the window rim.

It is another object of this invention to produce a sharpened outerwindow with a simple process minimizing the use of complex tools and thenumber of required processing steps.

It is yet another object of this invention to shape and sharpen athree-dimensional window in a tubular member of a rotatable surgicalinstrument with a single step process.

SUMMARY OF THE INVENTION

These and other objects of this invention are achieved by the preferredembodiment disclosed herein which is a method of forming an opening atone end of an elongated tubular surgical shaver blade having a distalend and a proximal end. The method comprises the steps of providing anelectrochemical grinding apparatus having a rotatable abrasive wheelwhich has a perimetral surface with a circumferential groove formed inthe surface. The groove has a predetermined arcuate profile in a radialplane of the wheel. The method further comprises securing the distal endof the elongated tubular surgical shaver blade in a predeterminedorientation relative to the wheel and moving the distal end of theshaver blade relative to the wheel during the performance of anelectrochemical grinding process.

In another aspect the invention lies in a method comprising the steps ofinclining the tubular members at a predetermined angle relative to thewheel and moving the closed, rounded ends of the tubular memberstangentially over the arcuate perimetral surface of the wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of the distal tip of a prior art outertube having a curvilinear cutting window.

FIG. 2 is an end view of FIG. 1.

FIG. 3 is a plan view of FIG. 1.

FIG. 4 is a side elevational view of a distal tip of an outer tubeformed in accordance with the principles of this invention.

FIG. 5 is an end view of FIG. 4.

FIG. 6 is a plan view of FIG. 4.

FIG. 7 is a front perspective view of the outer member shown in FIGS.4-6 with a chosen inner member.

FIG. 8 is a diagrammatic plan view of FIG. 7.

FIG. 9 is a sectional view of FIG. 8 taken along the line 9--9.

FIG. 10 is a sectional view of FIG. 8 taken along the line 10--10.

FIG. 11 is a sectional view of FIG. 8 taken along the line 11--11.

FIG. 12 is a sectional view of FIG. 8 taken along the line 12--12.

FIG. 13 is a diagrammatic elevational view in cross-section of anapparatus and method step incorporating the principles of thisinvention.

FIG. 14 is a sectional view of FIG. 13 taken along the line 14--14.

FIG. 15 is a view of the method and apparatus of FIG. 13 in a differentstage of the process of this invention.

FIG. 16 is a sectional view of FIG. 15 taken along the line 16--16.

FIG. 17 is a view of FIG. 15 taken at a different stage in the processof the invention.

FIG. 18 is an end view of FIG. 4 taken along the line 18--18 showing theprofile of the tip viewed along a line angled relative to its axis.

FIG. 19 is a diagrammatic front elevational view of an electrochemicalgrinding apparatus used in a preferred embodiment of the invention.

FIG. 20 is a view of FIG. 19 taken along the line 20--20.

FIG. 21 is an enlarged view of a portion of FIG. 20.

FIG. 22 is a side elevational view of the distal end of a prior arttoothed outer member.

FIG. 23 is a cross-sectional view of FIG. 22 taken along the line23--23.

FIG. 24 is a cross-sectional view of FIG. 22 taken along the line24--24.

FIG. 25 is a side elevational view of the distal end of an outer tubularmember constructed in accordance with the principles of this invention.

FIG. 26 is a cross-sectional view of FIG. 25 taken along the line26--26.

FIG. 27 is a cross-sectional view of FIG. 25 taken along the line27--27.

FIG. 28 is a side elevational view of an apparatus used in the method ofproducing a toothed outer such as that shown in FIG. 25.

FIG. 29 is a front elevational view of FIG. 28.

FIG. 30 is an enlarged view of a portion of FIG. 29.

FIG. 31 is a side elevational view of the components of FIG. 28 showinga portion of the method of producing the toothed outer member of FIG.25.

FIG. 32 is a view of FIG. 31 at a different portion of the method.

FIG. 33 is an exploded view of FIG. 30 showing in phantom the pathfollowed by various portions of the outer tubular member during themanufacturing process.

FIG. 34a through 34g show various positions of the components of theinvention during various portions of the method used to form the toothedouter tubular member.

FIG. 35a and 35b show cross-sectional views of a prior art rotatablesurgical shaver having an outer tubular member such as that shown inFIGS. 22-24 and an inner tubular member having a cutting window formedby a straight cut.

FIG. 36a and 36b are cross-sectional views of a rotatable surgicalshaver utilizing an outer tubular member constructed with the principlesof this invention and a prior art inner tubular member having a cuttingwindow with a straight cut.

FIG. 37 is a cross-sectional view of an inner tubular member during aprocess of forming sharpened edges around an opening of the member.

FIG. 38 is a side elevational view of FIG. 37.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 2 show a distal tip of a prior art outer tubular member 10of a rotary shaver blade assembly (not to scale). The proximal ends ofthe tubular member are conventional and well understood by those skilledin the art. Outer tubular member 10 has a distal tip 12 with acurvilinear cutting window 14 which faces to the side, i.e. laterally,perpendicular to axis 15, and away from the end of the blade, i.e.longitudinally in a direction parallel to axis 15. The terms "laterally"and "longitudinally" mean that the interior of the outer tubular memberis visible when viewed from these vantage points. The window has aperipheral rim 16 which is formed by the intersection of the window withthe interior surface 17 of the outer tube and is surrounded by a land 18which is angled at its distal end at an angle A relative to axis 15 andthe distal tip of window periphery 16. Angle A appears to be formed by acomplex grinding or shaping process and appears to be uniform along theextent of the land surface. Thus, land 18 lies at angle A relative tothe rim at each point along periphery 16. It is noted that proximal end20 of window 14 is not provided with an angled land at all, thusresulting in portion 19 which is simply the end facing surface of theouter tube wall which is exposed by the cut forming window 14. Thecurvilinear profile of window 14 is best seen in FIG. 1 as comprisingthree sections: a first section 21 extending from the proximal end 20 ofthe window to a first predetermined point P1, and having a radius ofcurvature R1; a second section extending from point P1 to apredetermined point P2 adjacent the distal end of the window, thissecond section 22 having whatever blended radius of curvature R2 whichis necessary to smoothly join the radiused section 21 to a third section23 which is a linear portion extending at some angle B relative to axis15. The window thus formed is best seen in FIG. 3 as having a relativelyrectangular shape with rounded proximal and distal ends and generallyparallel sides. Window 14 is formed by a process having at least twosteps: a first step requiring passing a cutting tool through the distaltip of tube 10 along the curvilinear profile shown in FIG. 1 and asecond step requiring the formation of land 18.

The subject invention relates to an improved outer tube 30 and a processfor forming the tube as shown in the remaining drawings. Referring toFIGS. 4 and 5, outer tube 30 has a distal end 32 provided with acurvilinear window 34 having a peripheral rim 36. The proximal end oftube 30 is conventional and forms no part of this invention. Window 34is surrounded by a peripheral land 38 angled at its distal and proximalends 39 and 40, respectively, at an angle C relative to the axis 42 ofthe outer tube. It will be noted that land 38 is, unlike the prior artembodiment discussed above, angled around the entire periphery of thewindow although points intermediate the distal and proximal ends 39 and40 may be at angles other than angle C as will be understood below. Asbest seen in FIG. 6, window 34 is less rectangular than window 14 of theprior art embodiment and has more of a pear-shaped or generallyelliptical outline with a large rounded distal end 44, a smaller roundedproximal end 46 and non-parallel sides. It should also be noted that theinvention facilitates creation of a large window while maintaining adistal bearing tip 48 on axis 42. Tip 48 may act as a bearing surfaceagainst the exterior surface of the inner member.

FIG. 7 is a front perspective view of the distal tip of outer tubularmember 30 assembled with an inner member 50 having a cutting window 51although it will be understood that a variety of inner cutting windowprofiles could be used. To facilitate the explanation of the invention,FIG. 7 is presented in diagrammatic plan view in FIG. 8 showing thevarious points at which cross-sectional views shown in FIGS. 9 through12 are taken.

The particular form of cutting edge provided on inner member 50 has apair of inwardly facing cutting surfaces 52 and 54 created on eitherside of inner window 51. Since each cutting surface 52 and 54 is closeto if not exactly tangential with the interior surface of the inner tube(best seen in FIG. 10) and extends proximally from the distal tip of theinner tube, the inner window has a generally rectangular opening whenviewed from the front. The inner window is formed, for example, by awire EDM process in which the wire is longitudinally extending at apredetermined angle to the axis of the inner member and follows agenerally rectangular path (viewed from the end of the tube). This pathproduces a tangential cutting surface at only certain points (i.e. atFIG. 10 but not at FIG. 9). The relationship of the cutting surfaces 52and 54 relative to adjacent portions of outer window 34 is better seenby reference to FIGS. 9 through 12 which show sectional views throughvarying portions of FIG. 8. It will be noted that the angle of land 38relative to a horizontal plane through axis 42 varies depending upon thelongitudinal placement of the point on the land at which the angle ismeasured. Thus, as shown in FIG. 9, the edge of outer window 34 isfairly sharp because the wall of the outer tube is cut at a relativelylow included angle compared to the angle of land 38 at other points,such as the point shown in FIG. 10. Similarly, the angle of land 38 atthe point represented by FIG. 11 is different still and the angle shownin FIG. 12 is the angle C referred to above. It will be further notedthat the relatively low included angle forming the cutting edge of theinner cutting window, i.e. the intersection of surfaces 52 and 54 withthe outside surface of inner member 50 results in a sharp edge in theareas of FIGS. 9 and 10. The curvilinear contour of outer window 34 incombination with the sharpness of its edges along rim 36 and the edgesof the inner window produces efficient tissue resection.

One process of forming the curvilinear contour of window 34 at distaltip 32 is best understood by reference to FIGS. 13 through 18. Theprocess utilizes a contouring apparatus such as an electrical formingdevice capable of creating an arcuate surface in another body. Theembodiment disclosed utilizes a plunge-type conventional computernumerically controlled (CNC) EDM device 100 incorporating a basin (notshown) for holding dielectric fluid 102, a work piece holder 104 andforming electrode tool 106 mounted to the EDM upper platen. A pluralityof hollow outer tubes 110 are attached in a vertical orientation toopposite sides of holder 104, each outer tube having a closed top end112 and an open bottom end 114. Holder 104 is attached to a base 116mounted to the EDM lower platen, the base being provided with aplurality of fluid channels 117 and 118 aligned with the open ends ofassociated tubes 110. While only two tubes 110 are shown in FIG. 13, itwill be understood that additional tubes are arranged on holder 104 intwo parallel rows 120 and 122 which may extend perpendicularly to theplane of the paper. Similarly, tool 106 is an electrode having atrapezoidal cross-section, best seen in FIG. 13, extendingperpendicularly to the plane of the paper and above holder 104. Theangled sides 130 and 132 of tool 106 are each provided with a pluralityof parallel channels 134 having arcuate profiles oriented at angle Crelative to the axes of the tubes in rows 120 and 122, each having aradius of curvature R3, best seen in FIG. 14, which ultimately interactswith outer tubes 110 to create the unique profile of window 34. It willbe understood that the channels could have other than circular profiles.

As shown in FIG. 15, electrode tool 106 is first moved down to aselected level between the parallel rows 120 and 122 of outer tubes 110and then laterally toward one of the rows, the rate being determined bythe machine control parameters in order to have the distal tip of outertubes 110 contact a selected channel 134. While a plurality of channelsare provided on each surface 130 and 132, not all portions of allchannels need to be used at any one time and the tool may be shiftedaround by proper programming of the CNC machine to utilize selectedportions of the channels and selected channels as will be understoodbelow. For example, any given channel 134 may be thought of as having aplurality of adjacent sections 140, 141, 142 and 143. The verticalpositioning of electrode 106 could be, for example, set to havelower-most section 140 be the active section. As the electrode continuesto move laterally a predetermined distance to a selected point, the EDMprocess forms an opening in each of the outer tubes while dielectricfluid is flushed through channels 118 and out the opening created at thedistal tip. During machining, electrical discharge parameters aremodified under program control so as to minimize cycle time whilemaintaining acceptable surface finish and edge sharpness on the finishedproduct. The pressurized dielectric fluid introduced by the timedflushing port reduces the machining time by removing swarf from themachining zone. The opening is defined by the intersection of thecylindrical tube wall at the rounded, closed end of the tubes with thearcuate profile of channels 134.

When the tool has been moved laterally a programmed distance to form thedesired window 34, the direction of the tool is reversed to approach row122 and the channels along surface 132 are brought into engagement withthe outer tubes in row 122 in order to produce the chosen profiles inthose tubes.

It will be appreciated by those skilled in the art that while tool 106has a relatively simple shape and moves in a relatively simple pattern,the intersection of the tool with the outer tube produces a resultantcomplex profile. Rather than being defined by a complex shape requiringseveral processing steps for its formation, window 34 has a simplearcuate profile when viewed in FIG. 16, or better still, when viewedalong a line at an angle C to the tube axis as best seen in FIG. 18. Theintersection of the arcuate channel profile with the cylindrical tuberesults in cutting edges with low included angles thereby making asubsequent sharpening operation unnecessary. The shape of the surface ofany given land 38 surrounding rim 36 and the shape of the associatedactual window 34 may be considered as being defined by the locus of allpoints lying at the intersection of an elongated, transversely arcuatesurface with the cylindrical body of the tube oriented at apredetermined angle relative to the transversely arcuate surface. Putanother way, the definition of the perimeter of window 34 may be thoughtof as the intersection of a cylindrical body with an imaginary surfacehaving a predetermined, symmetrical, concave arcuate profile. Inpractice this imaginary surface is defined by the concave surface ofchannel 134 and is considered endless because the surface extendsentirely through the cylindrical body enough to form a window therein.In the preferred embodiment, however, the activatable sections (140,etc.) of the surface of channel 134 lie on this imaginary surface andneed only subtend a lateral or transverse distance approximately greaterthan or equal to one-half the outside diameter of the cylindrical bodyin order to form land 38. If the imaginary surface is linearly extendedin a direction which is aligned with the axis of the tube, and if thearcuate profile transverse to the axis is a simple concave radius, theresultant locus of points defines convex land 38 (complementary to theconcave radius). If some other orientation or profile is used, the locusof points will produce a different shape.

The transverse curvature of window 34 when viewed as shown in FIG. 16 isthe same as that shown in FIG. 18. While the arcuate profiles ofchannels 134 are at a constant radius of curvature along the length ofthe channels, it will be understood that the radius of curvature mayvary along the channel length and/or the arcuate surface may have acontour other than circular extending along the axis line.

Because the shape is two-dimensional when viewed axially to thecylindrical surfaces 130 and 132 of the tool, complex shaped tooling orsimultaneous programmed machine motions are not required. The shape ofthe tool may be machined by using CNC wire EDM, or produced byconventional or electrochemical grinding using a wheel onto which theproper radius has been dressed. Similarly, plunge type EDM or ECM may beused with the part contour being produced by contours on the tooling.Tooling cost is low due to the simple profile and, because complexmachine motions are not required, simultaneous multiple part machiningis readily implemented.

A preferred process of forming the curvilinear contour of window 34 atdistal tip 32 is best understood by reference to FIGS. 19-21. Thisprocess utilizes a cylindrical forming apparatus which, in the preferredembodiment, is a conventional electrochemical grinding machine (ECG)which has had the perimetral (circumferential) surface of its abrasivegrinding wheel shaped to ultimately form the contour of window 34. Itwill be understood that the processes disclosed herein could be used toform an opening in a previously closed distal end of a tubular member,or could be used to shape or sharpen an opening previously formedtherein.

Electrochemical grinding machine 200 comprises a grinding wheel 202, abase (not shown) for supporting a table 206 movable relative to the baseand wheel under programmable control. A nozzle 208 directs electrolyte210 at the work location adjacent wheel 202 in a conventional manner.The operation of the machine components, processes, table motion, speed,etc. is controlled in a conventional manner. Table 206 receives a jig212 to hold a plurality of tubular members 220 in an inclinedorientation relative to a line tangent to wheel 202. The tubular members220 are electrically conductive and serve as one electrode within theapparatus (the wheel acting as the other electrode). Each member 220 hasa closed distal tip 32 into which a window 34 (as shown in FIGS. 4-6)will be formed as explained herein. The tubular members 220 are inclinedat an angle C which is the same as the angle between the tubular axisand the face of the channels of tool 106 as shown in FIG. 13. As table206 moves in direction 222 the distal tips of successive tubular members220 will move tangentially past wheel 202. Perimetral surface 230 ofwheel 202 is provided with a groove 232 having the selected profilewhich in this embodiment is a simple radius of curvature R3, the sameradius as that of channel 134 shown in FIG. 14. Groove 232 is best seenin FIG. 21 which shows a view of the wheel groove within essentially aradial plane of the wheel. Moving table 206 along a linear path ofmotion in the plane of wheel 202 to tangentially intersect distal tips32 of tubular members 220 with the groove at the wheel periphery duringactivation of the electrochemical process will produce in each tip acurvilinear window 34 as shown in FIGS. 4-6 and 18 without anyadditional shaping or sharpening process. While jig 212 and table 206are shown in the drawings to fixedly hold each tube in a fixedorientation relative to wheel 202, as will be explained below the tubescould be supported on jig 212 in a movable manner and the table couldmove along a complex path of motion (other than simply in one lineardirection). The movement of the tubes relative to the jig or themovement of the table relative to the base could be continuous orindexed (to discrete positions) under programmable control. While theapparatus of FIGS. 19-21 utilizes electrochemical grinding, similarwheel shapes and motions may be applied to conventional grinding orother processes.

While the device and process disclosed have been described in terms ofan outer, stationary tubular member, it will be understood by thoseskilled in the art that the cutting edge of an inner, rotating tubularmember may also be formed in accordance with the principles of theinvention disclosed herein. Appropriate changes may be necessary in theshapes and sizes of the electrode tool 106 or the wheel 202, supportingjigs and paths of travel, depending upon the desired shape of the innercutting edge. One such device and process is disclosed below in FIGS. 37and 38.

Furthermore, the window shape of the preferred embodiment of the outertube disclosed herein is such that a linear tangential motion of theinclined tubular members 220 relative to wheel 202 is the desired motionto produce the desired shape. Variations in window shape or cuttingedges in either the inner or outer members may require otherorientations of the tubular members or other than linear motion of table206.

Also, as briefly mentioned above, the path of motion of the tubesrelative to the wheel may change depending upon the desired shape to beformed in a tubular member. For example, the tube may be moved invarying directions other than linear and/or it may be rotated about itsaxis as it moves past the wheel, moved up and down relative to the wheelon any given pass to change the depth of the cut in the tube, etc.Additionally, the machine could have different ECG stages, each with adifferent wheel so that a complex table path of motion would passdifferently shaped wheels to produce complex cuts and different shapes.Another example may be a tube formed by a plurality of linear passes.That is, the tube could be moved linearly relative to a wheel asdescribed above, rotated about its axis, moved linearly again, rotatedagain, moved again, etc. The wheel in such case could even have a flatperipheral surface to produce an opening approximating window 34. Withappropriate indexing and motion of the tubular member in all dimensionsrelative to the jig (e.g. linearly along its axis, rotating about itsaxis and about another axis transverse to its axis) and with appropriateindexing and motion of the table relative to the wheel (or relative todifferent wheels if additional stages are used), it would be possible toproduce cuts of almost any imaginable shape, depth, angle and lengthsuch that this method would even make it possible to produce cuttingteeth in the tubular member. This latter method could be analogous tocreating a complex shape by a CNC (computer numerical control) millingmachine operating with several degrees of freedom and would result in atoothed opening in either an inner or outer tubular member of a rotatingsurgical shaver.

One method of forming the cutting teeth in a tubular member is shown inFIGS. 22 through 36. As shown in FIGS. 22-24 a prior art outer tubularmember 300 has a distal tip 302 comprising a cutting window 304 boundeda plurality of teeth 306 in two, parallel and longitudinally extendingrows 307 and 308. The cutting window and teeth of such an outer tubularmember 300 may be formed, for example, by a conventional EDM process inwhich the cut is made transversely through the distal tip of the tubularmember so that the top edges 309, 310 of teeth in opposing rows 307, 308are coplanar at corresponding transverse points and the troughs 312 and314 between adjacent teeth in opposing rows are also coplanar. Theincluded angle of each tooth is bounded by the horizontal surface 309(or 310, depending on the row) and the inner surface 311 of the tube.

As shown in FIGS. 25 through 27 outer tubular member 330 constructed inaccordance with the principles of this invention has a toothed profileconsiderably sharper than that of prior art tubular member 300. Outertubular member 330 has a distal tip 332 in which a cutting window 334 isformed which is bounded by a plurality of teeth 336 in two, parallel andlongitudinally extending rows 337 and 338. As with the prior art device,the teeth 336 in one row are transversely coplanar with thecorresponding teeth in the opposite row. The top edges 339 and 340 ofeach tooth 336 are curved to produce points 342 and 344. Troughs 346 and348 between adjacent teeth are also curved but at a different profile aswill be understood below. The included angle between edge 339 and theinner surface 341 is smaller than the corresponding angle of the priorart device 300.

Cutting window 334 has a land 350 entirely surrounding the window, theland being angled relative to the window periphery so that there is asharp edge on the radially innermost side adjacent to the opening. Theincluded angle between the land surface and the inner surface 341 variesdepending upon the longitudinal position of the point where the angle ismeasured. For example, the included angle at edge 339 is smaller thanthat at trough 346. Land 350 comprises a proximal land section 352 and adistal land section 354, the shapes of which are shown diagrammatically.It will be understood that, while an inclined land surface will surroundwindow 334, the actual shape of this land may vary from that shown inFIG. 25 depending upon the actual tool used.

FIGS. 28-33 and 36 show an apparatus and method for producing thetoothed outer tubular member 330. Wheel 400 and jig 402 are part ofelectrochemical grinding machine similar to that shown in FIG. 19. Theremaining components (table, electrolyte nozzle, etc.) are omitted forclarity. Wheel 400 has a predetermined thickness 404 and a predeterminedperimetral surface 406 which is dressed with a plurality of notches 408and proximal and distal angled surfaces 410 and 412, respectively, toform the various teeth 336 and proximal and distal land sections 352 and354 as will be understood below. The shapes of surfaces 410 and 412 incombination with the motions of various components will affect the shapeof proximal and distal land sections 352 and 354. The various cuts inthe perimetral surface 406 have a radially outermost portion (extent)416 and a radially innermost portion (extent) 417. The shape of theperimetral surface may be changed to produce a variety of cuts in aworkpiece 420 as will be understood below.

Jig 402 supports a rotatable housing 430 which is adapted to rotateabout an axis 432 parallel to wheel axis 414. Extending from the frontface 434 of housing 430 is a tubular workpiece 420 which has a distaltip 436 and an axis 438 which is aligned parallel to and offset by adistance D from axis 432 as best seen in FIGS. 28 and 30. The distance439 between axis 432 and the radially innermost portion 416 is less thanthe sum of the radius T of the tubular member and the distance D betweenthe tubular member axis 438 and housing axis 432. Wheel 404 is adaptedto rotate about fixed axis 414 while the workpiece 420 is adapted tomove in an eccentric pattern about axis 432. As shown in FIGS. 29-33,the workpiece does not rotate about its axis 438 but rotation of housing430 about axis 432 causes the workpiece axis 438 to be placed atvariable radial distances from the wheel axis 414 such that differentparts of the workpiece 420 will intersect the perimetral surface 406 ofthe wheel at different points. The eccentric motion of workpiece 420about axis 432, as best seen in FIG. 33, causes points at varying radialdistances from axis 432 to rotate along different circular paths. Thus,the circular path 441 is that defined by points on workpiece 420 thatrotate about axis 432 at a radial distance from axis 432 equal to thedistance between axis 432 and innermost portion 417 of the wheel'sperimetral surface. Similarly, the circular path 442 is defined bypoints on workpiece 420 that rotate about axis 432 at a radial distancefrom axis 432 equal to the distance between axis 432 and outermostportion 416. It will be understood that various parts of the workpiecerotate along curvi-linear paths, in this case circular paths havingradii between paths 441 and 442. As shown in FIG. 34a-g the rotation ofworkpiece 420 relative to wheel 402 proceeds in various stages untilultimately, in FIG. 34g, an outer tubular member 330 is produced.

The sharper teeth of an outer tubular member that can be easily producedwith this method produce a sharper rotatable surgical shaver. As shownin FIG. 35, a prior art surgical shaver comprising an outer tubularmember 300 and inner tubular member 301 is limited in sharpness. Outertubular member 300 is identical to that shown in FIGS. 22-24. Innertubular member 301 is shown also with a straight cut through its cuttingwindow so that all of the cutting surfaces lie in parallel planes P1 andP2 (parallel to the plane of the inner window), as best seen in FIG.35a. (Note that a sharper inner member 50 is shown in FIGS. 8-11 withcutting surfaces 52 and 54 in parallel, longitudinal planes which areperpendicular to the inner window. Member 50 could be combined withouter member 300.) When inner member 301 is rotated relative to theouter member 300, the movement of cutting surface 351 past cuttingsurface 308 creates a shearing action. The actual cut occurs at thejunction of the radially innermost edge of surface 308 and the radiallyoutermost edge of surface 351. Because of the straight cuts used to formthe cutting windows of such prior art devices, the included angle ofthese edges is large and, therefore, their sharpness is limited.

On the contrary, as shown in FIG. 36, simply replacing a conventionalouter member 300 with an outer tubular member 330 constructed inaccordance with the principles of this invention will increase thesharpness of the junction between the radially innermost edge of surface339 and the radially outermost edge of surface 351 thereby producing asmaller included angle and a sharper cut. It will be understood thatinner member 350 may be produced with a toothed or untoothed cuttingwindow. In either case, the cross-section of the inner member shown inFIG. 35 and 36 will be similar.

The sharpened, non-toothed inner member shown in FIGS. 8-11 as innermember 50 could also be combined with outer member 350 to produce asharper cutting action than that offered by the combination of FIG. 35.If the inner member is additionally provided with teeth that aresharpened to a point at the radially outermost portion of each tooth(adjacent the inner edge of surface 308 or 339) the sharpness of the cutwill be even further enhanced.

One method of forming such a sharpened toothed or non-toothed innermember is shown in FIGS. 37 and 38 in which an electrochemical grindingmachine or an electrical discharge machine may be used to producesharpened edges or teeth in the cutting window of an inner tubularmember 500. Tool 502 could be a rotating wheel in the case ofelectrochemical grinding machine or a non-rotating electrode in the caseof a electrical discharge machine. In each case the tool has a diametersmaller than that of the tubular member so the sharpened edge is formedon the radially outermost surface of the member. Moving the tool towardinner member 500 such that the intersection of tool 502 with the outersurface of tubular member 500 would produce opposing sharpened outeredges 504 and 506. The edges could be produced with or with out teeth.It will be understood that replacing member 350 of FIG. 36 with innertubular member 500 will replace flat surface 357 with an angled surface508 thereby producing a sharper cut.

It will be understood by those skilled in the art that numerousimprovements and modifications may be made to the preferred embodimentof the invention disclosed herein without departing from the spirit andscope thereof.

What is claimed is:
 1. A method of forming at least one opening in apredetermined portion of a tubular member of a surgical shaver, saidpredetermined portion having an axis, said method comprising the stepsof:(a) providing a hollow tubular member having an axis, a distal endand a proximal end; (b) providing a grinding wheel having an axis and aperimetral surface provided with a predetermined profile; (c) orientingsaid axis of said predetermined portion of said tubular member in apredetermined first position relative to said grinding wheel; (d)rotating said grinding wheel about its axis; (e) moving said tubularmember and said grinding wheel relative to each other in a first lineardirection to form at least a portion of the opening in saidpredetermined portion of said tubular member; (f) rotating said tubularmember about its axis to a predetermined second position relative tosaid grinding wheel; and (g) moving said tubular member and saidgrinding wheel relative to each other in a second linear direction toform another portion of the opening in said predetermined portion ofsaid tubular member.
 2. A method according to claim 1 wherein saidprofile is adapted to produce in said tubular member at least one toothhaving a tooth trough and adjacent tooth sides and wherein said axis ofsaid tubular member is parallel to said axis of said grinding wheel. 3.A method of forming at least one opening in a predetermined portion of atubular member of a surgical shaver, said predetermined portion havingan axis, said method comprising the steps of:(a) providing a hollowtubular member having an axis, a distal end and a proximal end; (b)providing a grinding wheel having an axis and a perimetral surfaceprovided with a predetermined profile; (c) orienting said axis of saidpredetermined portion of said tubular member in a predetermined firstposition relative to said grinding wheel; (d) rotating said grindingwheel about its axis; (e) moving said tubular member and said grindingwheel relative to each other in a first arcuate direction to form atleast a portion of the opening in said predetermined portion of saidtubular member; (f) rotating said tubular member about its axis to apredetermined second position relative to said grinding wheel; and (g)moving said tubular member and said grinding wheel relative to eachother in a second arcuate direction to form another portion of theopening in said predetermined portion of said tubular member.
 4. Amethod according to claim 3 wherein said profile is adapted to producein said tubular member at least one tooth having a tooth trough andadjacent tooth sides and wherein said axis of said tubular member isparallel to said axis of said grinding wheel.
 5. A method of forming atleast one opening in a predetermined portion of a tubular member of asurgical shaver, said predetermined portion having an axis, said methodcomprising the steps of:(a) providing a hollow tubular member having anaxis, a distal end and a proximal end; (b) providing a grinding wheelhaving an axis and a perimetral surface provided with a predeterminedprofile; (c) orienting said axis of said predetermined portion of saidtubular member in a predetermined first position relative to saidgrinding wheel; (d) rotating said grinding wheel about its axis; and (e)moving said tubular member and said grinding wheel relative to eachother to form said opening.
 6. A method according to claim 5 whereinsaid relative motion is linear.
 7. A method according to claim 5 whereinsaid relative motion is arcuate.
 8. A method according to claim 5wherein said predetermined profile on said perimetral surface comprisesat least one circumferential notch adapted to produce a toothed openingin said tubular member.
 9. A method according to claim 5 wherein saidaxis of said tubular member is parallel to said axis of said grindingwheel and wherein said moving step further comprises:(f) moving saidpredetermined portion of said tubular member transversely within a planeperpendicular to the axis of said grinding wheel sufficiently to form atleast a portion of said at least one opening; (g) moving said tubularmember a predetermined distance longitudinally along its axis; and (h)repeating step (f).